1. Field of the Invention
The present invention relates to a semiconductor device, and in particular, to a semiconductor device that handles differential signals.
2. Description of the Related Art
In various electronic devices, transmission of data using differential signals is being utilized for the purpose of reducing laid-out signal lines, or of increasing noise tolerance. For example, in laptop personal computers, folding mobile phones, or the like, a differential signal, known as a Low Voltage Differential Signal (referred to below as LVDS) or a Reduced Swing Differential Signal (referred to below as RSDS), is used for transmitting and receiving signals to and from a first casing in which operation buttons and the like are mounted, and a second casing in which a liquid crystal panel is mounted. Since high speed transmission and low power consumption are possible, the LVDS and the RSDS are distinguished by having excellent EMI (Electromagnetic Interference) characteristics, due to transmitting signals of small amplitude. For example, related technology is described in Patent Documents 1 and 2.    Patent Document 1: Japanese Patent Application Laid-Open No. H6-104936    Patent Document 2: Japanese Patent Application Laid-Open No. 2000-59443    Patent Document 3: Japanese Patent Application Laid-Open No. 2006-49695
In signal transmission using a differential signal, a digital value of 1 or 0 is converted into a signal pair having mutually reverse phases, to be transmitted. Here, if balance of electrical characteristics, such as length of signal path along which the signal pair is transmitted, or parasitic capacitance or parasitic resistance of the path, is lacking, problems occur in that symmetry of waveform of the signal pair is lost, transmission rate decreases, and the EMI deteriorates. The present inventors recognized a problem in that waveform of a differential signal deteriorates in cases in which a circuit for inputting and outputting the differential signal is configured as a Ball Grid Array (BGA) package, as described in Patent Document 3.